Certain types of cancers such as breast cancers, particularly inflammatory and locally advanced tumors, often resist traditional treatments. It has been statistically shown that sixty to seventy percent of victims of such breast tumors do not survive past five years. The efficacy of conventional methods of treating cancer, such as radiotherapy and chemotherapy, is limited due to necessary constraints on dosage amounts for safety. For example, it is known that chemotherapy can be applied in sufficient amounts to kill virtually all cancer cells of a tumor. However, the amounts of chemotherapy needed to achieve this can be high enough to cause poisoning of the patient and/or undue side effects. As another example, the intensity of an x-ray beam applied in accordance with radiotherapy cannot be so high as to damage nearby critical organs and surrounding healthy tissues. Accordingly, there is an ongoing need to develop techniques that enhance existing cancer-related therapeutic procedures so as to increase their effectiveness without increasing the risk of damage to healthy tissue and causing additional discomfort for cancer patients.
One recent approach toward improving cancer therapy is to subject a tumor to a hyperthermia treatment. The application of heat to cancer cells has been found to increase the efficacy of certain types of therapies for various proposed reasons. Microwave and radio frequency (RF) energy sources have been employed to conduct hyperthermia treatment. Microwave energy has been applied to tumors using waveguides. However, the relatively high frequencies at which microwaves propagate are not suitable for deep penetration into tissue. RF energy has also been utilized in some instances, and has the potential to achieve greater penetration due to relatively lower frequencies. However, both microwave and RF techniques have in the past required the use of invasive elements, such as wires, catheters, lumens, probes, receivers, and the like. These invasive elements are typically inserted or embedded in the tumor to be treated to ensure proper coupling and focusing of the electromagnetic energy at the tumor site. The use of invasive elements adds complexity to the procedure and is a source of discomfort for patients. Examples of invasive heating techniques using microwave and RF energy are disclosed in U.S. Pat. Nos. 5,928,159; 6,275,738; 6,358,246; 6,391,026; and 6,468,273.
It therefore would be desirable to provide a method and apparatus for non-invasively inducing hyperthermia in a tumor by applying electromagnetic energy, and preferably RF energy, to the tumor in a controllable, coherent manner, and while avoiding or reducing problems associated with conventional techniques.